dropping out of VTEC when shifting
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From: Longmont, CO
Originally Posted by negcamber' date='Mar 24 2007, 09:55 PM
Quite a bit of the power is being spent on spinning the flywheel only.
Regarding the scenario of revving the engine while in neutral - sure, open up the throttle and the engine's entire output goes into spinning up the flywheel. You have to understand however, that is NOT at all what's happening during a shift, when revs FALL. During the shift, the flywheel LOSES energy. It's rotational kinetic energy turns into a higher rotational kinetic energy of the drivetrain.
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From: Dry Branch
Originally Posted by negcamber' date='Mar 24 2007, 09:55 PM
Thanks for weighing in Red...
Absolutely, it is rare to completely eliminate slip when shifting. However nornally the clutch slip on up shift is extremely short lived as the clutch catches up very quickly.
For the AP2...at redline in 1st, the corresponding rpm in 2nd is ~5200rpm. And we can see in the video that the engine is spinning at 6k+ when shifting 1-2 with the CDV in place. So there is at least 800rpm differential between the flywheel and the clutch.
So the question is...how much power loss is there when the clutch is slipping that much. Elistan says almost none (aside from heat transfer) and I don't see how that is possible with that much slip.
Absolutely, it is rare to completely eliminate slip when shifting. However nornally the clutch slip on up shift is extremely short lived as the clutch catches up very quickly.
For the AP2...at redline in 1st, the corresponding rpm in 2nd is ~5200rpm. And we can see in the video that the engine is spinning at 6k+ when shifting 1-2 with the CDV in place. So there is at least 800rpm differential between the flywheel and the clutch.
So the question is...how much power loss is there when the clutch is slipping that much. Elistan says almost none (aside from heat transfer) and I don't see how that is possible with that much slip.
A good deal of heat would be generated, and that's a loss, but by keeping the engine in the fat part of the power band you'll make up more than you burn away.When you run an AP2 through the gears hard do you smell the clutch afterward?
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From: Dry Branch
Originally Posted by Elistan' date='Mar 24 2007, 10:52 PM
Actually, NONE of the power is going into the flywheel - the flywheel is actually slowing down! It's LOSING energy.
Regarding the scenario of revving the engine while in neutral - sure, open up the throttle and the engine's entire output goes into spinning up the flywheel. You have to understand however, that is NOT at all what's happening during a shift, when revs FALL. During the shift, the flywheel LOSES energy. It's rotational kinetic energy turns into a higher rotational kinetic energy of the drivetrain.
Regarding the scenario of revving the engine while in neutral - sure, open up the throttle and the engine's entire output goes into spinning up the flywheel. You have to understand however, that is NOT at all what's happening during a shift, when revs FALL. During the shift, the flywheel LOSES energy. It's rotational kinetic energy turns into a higher rotational kinetic energy of the drivetrain.
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From: Jacksonville, FL
Originally Posted by Elistan' date='Mar 24 2007, 10:52 PM
Actually, NONE of the power is going into the flywheel
If clutch slip is the situation where the flywheel is spinning faster than the clutch while the clutch is engaged, then what you say here is impossible. Even if the flywheel is slowing down, if it is spinning faster than the clutch then power that could be transmitted to the clutch is instead only being used to spin the flywheel. That power loss peaks at shift and decreases as the clutch speed approaches the flywheel speed.
And this happens at nearly every shift on every MT car. However, for most cars the time it takes for the clutch speed to match the flywheel speed is very short (almost feeling instintaneous). However, from the vid we can see that in the ap2, the clutch and flywheel have to make up a differential of 800+ rpm.
So...what is clutch slip?
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From: Dry Branch
Originally Posted by gardy' date='Mar 25 2007, 06:56 AM
I thought on AP2s that VTEC engages at 6000 on the way up and disengages at 5500 on the way down.
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From: Queen City, NC
If the AP2 actually drops to 5,400 on the 1-2 shift then I suspect Gardy is right, but even if the AP2 does drop out of VTEC it's not like having an AP1 drop below 5,800. You guys have a much flatter torque curve while the AP1's have a big bump in torque (that they need) once VTEC engages. Given the extra torque and the range over which it is available I doubt that dropping out of VTEC for a bit on a 1-2 shift will make any difference at all.
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From: Santa Monica-SoCal
i just watched a vid of a stock ap2 shifting and it all makes sense now.
the comptech flywheel makes all the difference as it makes my revs move fast, up and down. that's why i had trouble staying in vtec.
it still does technically fall out of vtec, but u prob won't feel it like u guys said.
the comptech flywheel makes all the difference as it makes my revs move fast, up and down. that's why i had trouble staying in vtec.
it still does technically fall out of vtec, but u prob won't feel it like u guys said.
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